FR3014691A1 - CAPSULES CONTAINING CELLS WITH HEMATOPOIETIC POTENTIALITY - Google Patents

Abstract

The present invention relates to a capsule comprising at least one cell with hematopoietic potential, said capsule being formed of a liquid core and at least one gelled envelope completely encapsulating the liquid core at its periphery, the use of such a capsule for the ex vivo production of enucleated erythroid cells as well as an ex vivo method of producing enucleated erythroid cells using said capsule.

Description

Capsules containing cells with hematopoietic potential The present invention relates to a capsule comprising at least one cell with hematopoietic potential, said capsule being formed of a liquid core and at least one gelled envelope completely encapsulating the liquid core at its periphery, the use of such a capsule for the ex vivo production of enucleated erythroid cells as well as an ex vivo method of producing enucleated erythroid cells using said capsule. There is still a high demand for labile blood products, particularly for transfusion purposes, and this demand is not satisfactorily met by the current supply of natural human blood. As a result, many substitutes for natural blood have been studied. However, recombinant or stabilized hemoglobins have shown disappointing performance, the indications of artificial oxygen carriers are limited and the development of "universal" red blood cells made compatible with the ABO system and / or the RhD antigen by enzymatic treatment or masking antigenic is slow. There is therefore a need for alternatives to these methods. In this regard, attempts to produce erythroid cells, such as red blood cells, from stem cells in vitro are particularly encouraged. However, it is a considerable challenge to replicate in vitro what it takes nature several months to build in vivo. During its development in humans, erythropoiesis evolves from the mesoderm into two waves. Primary erythropoiesis begins in the yolk sac (extra-embryonic tissue) in the third week of pregnancy and gives rise to nucleated megaloblastic primitive erythrocytes, which synthesize embryonic hemoglobin of the type Gower I g2c2) and Gower II (a2c2). . Final erythropoiesis begins during the fifth week of gestation in the mesonephric aorta gonad (AGA) region, before migrating to the fetal liver and bone marrow. The mature erythroid cells produce little by little, leading to the production of enucleated red blood cells (RBC), normocytic and containing fetal hemoglobin (a2y2) then adult (a2 [32]. To date, several attempts to produce red blood cells from human embryonic stem cells have been reported, as described by Ma et al. (2008) Proc. Natl. Acad. Sci. USA 105: 13087-13092. However, these experiments generally rely on a step of co-culture in the presence of stromal cells, which makes the intensification of the processes difficult.

For example, patent application WO2005118780 describes an in vitro method for the mass and selective production of enucleated erythrocytes. According to this method, the hematopoietic stem cells are cultured in a culture medium which comprises at least one hematopoietic growth factor and then the culture of the cells thus obtained is brought into contact with the support cells. The patent application WO2011101468 for its part describes a cell culture medium, without the requirement of a co-culture on a cellular stroma, for the growth and / or the differentiation of the cells of the hematopoietic line which comprises insulin. , transferrin and plasma or serum.

The method for industrial scale production of choice today is the stirred reactor, used for example for the production of vaccines or monoclonal antibodies, with growth of cells in solution or microparticles for adherent cells. This mode of production nevertheless poses problems since the crops are grown at high cell densities, which is necessary for industrial production. Indeed, the higher the density of cells, the greater the flow must be increased and shake accordingly. However, unlike yeasts and bacteria, mammalian cells, especially stem cells, are fragile and less resistant to these mechanical treatments leading to much lower yields than expected. Beads filled with alginate are used in cell culture, as a support for adherent cells where the cells are located outside the beads. Subsequently, the idea of encapsulating cells inside full alginate beads was discussed. A first problem of toxicity then appeared in the process of encapsulation and many developments on the material and the gelling process have been proposed to improve the viability of the cells thus taken in the alginate matrix (A method for the Keywords: Enamel, Naohito Kondo, Toshikazu Takano, Kaneo Suzuki, Kotoo Suzuki. ). A second problem is the lack of space inside the gel for cell growth. Various strategies have therefore been tested with regard to the formation of capsules (Encapsulation of biological material, Franklin Lim, US 4352883, 1982, Tissue culture and production in permeable gels, Elizabeth Maureen Frye, Mark Maurice Lynch, John Paul Vasington, EP0185701, 1984). .

The patent application WO 2010/063937 describes a process for the preparation of capsules having a liquid core and a thin gelled envelope completely encapsulating the core. These capsules are formed by coextrusion of drops at the exit of a double envelope. Said capsules are described as likely to contain cells. Nevertheless, even if the process seems suitable for cell encapsulation, there is no indication that the capsules make it possible to support cell growth when the encapsulated cells are cultured, and especially the amplification and differentiation of hematopoietic potential cells, in particular hematopoietic stem cells or erythroid progenitor cells.

The inventors have demonstrated that the capsules containing cells with hematopoietic potentiality according to the invention make it possible to solve all these problems and thus make it possible to envisage for the first time an application to the cell culture of cells with hematopoietic potentiality on a large scale. The object of the invention is thus to improve the yield of cell cultures of hematopoietic potential cells, to produce enucleated erythroid cells, in a bioreactor. The challenge is to bring nutrients and eliminate the catabolites necessary for the good growth of cells with hematopoietic potentiality. The capsule according to the invention makes it possible to protect said cells from shearing or oxygen bubbles in solution, while guaranteeing homogeneous conditions of growth. With a porous wall with small molecules and a size less than one millimeter, the diffusion is indeed sufficient to guarantee homogeneity in concentration inside the capsules. With the cell-protecting wall, it will be possible to agitate a large concentration of capsules effectively and extensively in the bioreactor. Encapsulation has other advantages for the culture of cells with hematopoietic potential on a large scale: the capsules are simple to handle (by sedimentation, capture through a filter) and will allow for example to easily change the medium of culture without applying stress on the cells, unlike a conventional reactor. Thus, the present invention relates to a capsule comprising a liquid core, a gelled envelope completely encapsulating the liquid core at its periphery, the gelled envelope being adapted to retain the liquid core when the capsule is immersed in a gas, the gelled envelope comprising at least one gelled polyelectrolyte and at least one surfactant, the liquid core of which comprises at least one cell with hematopoietic potential.

By "cells with hematopoietic potential" is meant cells capable of differentiating to one or more of the lines that cause blood cells. More particularly, the "hematopoietic potential cells" according to the invention are cells of the erythroid line, capable of producing red blood cells during their differentiation. The cells with hematopoietic potentiality according to the invention may especially come from stem cells, in particular embryonic stem cells (ESC), adult stem cells, such as hematopoietic stem cells (HSCs), pluripotent induced stem cells (iPS), immortalized cells, erythroid progenitor cells or erythroid precursors. Preferably, the "hematopoietic potential cells" of the invention are human cells. Preferably, the cells with hematopoietic potential are hematopoietic stem cells and / or erythroid progenitor cells and / or erythroid precursors. When hematopoietic potential cells are hematopoietic stem cells, these are preferably human hematopoietic stem cells, particularly CD34 + cells that can be obtained from umbilical cord blood or by leukopheresis from peripheral blood. They will differentiate preferentially into reticulocytes and / or erythrocytes. Erythrocytes, or red blood cells, are more commonly known as red blood cells. Reticulocytes are the cells preceding the erythrocyte stage in erythropoiesis. They are almost similar to them. Reticulocytes are young red blood cells that still have ribosomes and mitochondria, but lack a peroxisome. By "erythroid progenitor cell" is meant a cell derived from the differentiation of a hematopoietic stem cell, capable of proliferating and differentiating into a cell of the erythroid line, in particular into reticulocytes and / or erythrocytes. They are preferably human erythroid progenitor cells.

By "erythroid precursor" is meant any cell of the erythroid line cytologically identifiable, that is to say meeting the conventional criteria for identifying cell types ranging from proerythroblast to acidophilic erythroblast. Is preferably human erythroid precursors. In the context of the present invention, the liquid heart of the capsule may comprise at the time of encapsulation an amount of cells with a hematopoietic potential of between 1 and 10,000, preferably between 10 and 1000 cells / capsule. The liquid heart of the capsule according to the invention consists of a preferably physiologically acceptable liquid, such as a saline solution, a physiologically acceptable viscosifier and / or a culture medium intended for the growth and differentiation of cells with hematopoietic potentiality. , whose composition will be detailed in the following description. The liquid heart may also include physiologically acceptable excipients, such as thickeners, or rheology modifiers. These thickeners are, for example, polymers, cross-polymers, microgels, gums or proteins, including polysaccharides, celluloses, polysaccharides, silicone polymers and co-polymers, colloidal particles (silica, clays). , latex ...). The gelled envelope of the capsules according to the invention comprises a gel containing water and at least one polyelectrolyte reactive with multivalent ions. According to the invention, the envelope further contains a surfactant resulting from its manufacturing process, as described below. In particular, the capsule according to the invention is obtained from a process comprising the following steps of: a) separate conveying in a double jacket of a first liquid solution containing at least one cell with hematopoietic potentiality and a second liquid solution containing a liquid polyelectrolyte suitable for gelation; b) forming, at the exit of the jacket, a series of drops, each drop comprising a central core formed of said first solution and a peripheral film formed of said second solution and completely covering the central core; c) immersing each drop in a gelling solution containing a reagent adapted to react with the polyelectrolyte of the film to change it from a liquid state to a gelled state and form the gelled envelope, the central core forming the liquid core; d) recovery of formed capsules; the second solution containing at least one surfactant prior to contact with the first solution.

According to one aspect of this method, the ratio of the flow rate of the first solution to the flow rate of the second solution at the outlet of the jacket is between 1 and 200, advantageously between 10 and 200, the gelled envelope having a thickness of between 0.1% and 10%, advantageously between 0.1% and 2% of the diameter of the capsule, after recovery of the capsules formed. In another aspect of the process, the drops formed by coextrusion in the jacket fall by gravity through a volume of air into the gelling solution. In the context of the present description, the term "surfactant" means an amphiphilic molecule having two parts of different polarity, one lipophilic and apolar, the other hydrophilic and polar. A surfactant may be of ionic type (cationic or anionic), zwitterionic or nonionic.

The surfactant is preferably an anionic surfactant, a nonionic surfactant, a cationic surfactant, or a mixture thereof. The molecular weight of the surfactant is between 150 g / mol and 10,000 g / mol, advantageously between 250 g / mol and 1500 g / mol. In the case where the surfactant is an anionic surfactant, it is for example chosen from an alkyl sulphate, an alkyl sulphonate, an alkyl aryl sulphonate, an alkaline alkyl phosphate, a dialkyl sulphosuccinate, an alkaline earth salt of saturated or unsaturated fatty acids. These surfactants advantageously have at least one hydrophobic hydrocarbon chain having a number of carbons greater than 5 or even 10 and at least one hydrophilic anionic group, such as a sulphate, a sulphonate or a carboxylate linked to one end of the hydrophobic chain. In the case where the surfactant is a cationic surfactant, it is for example chosen from an alkylpyridium or alkylammonium halide salt such as n-ethyldodecylammonium chloride or bromide, cetylammonium chloride or bromide (CTAB) . These surfactants advantageously have at least one hydrophobic hydrocarbon chain having a number of carbons greater than 5 or even 10 and at least one hydrophilic cationic group, such as a quaternary ammonium cation. In the case where the surfactant is a nonionic surfactant, it is for example chosen from polyoxyethylenated and / or polyoxypropylenated derivatives of fatty alcohols, fatty acids, or alkylphenols, arylphenols, or from alkyl glucosides, polysorbates, cocamides. In particular, the surfactant will be chosen from the following list: an alkyl sulphate, an alkyl sulphonate, an alkyl aryl sulphonate, an alkaline alkyl phosphate, a dialkyl sulphosuccinate, an alkaline earth salt of saturated or unsaturated fatty acids, a salt of alkylpyridium or alkylammonium halides such as n-ethyldodecylammonium chloride or bromide, cetylammonium chloride or bromide, polyoxyethylenated and / or polyoxypropylenated derivatives of fatty alcohols, fatty acids or alkylphenols, or from arylphenols, alkyl glucosides, polysorbates, cocamides or mixtures thereof. More particularly, the total weight percent of surfactant in the second solution will be greater than 0.01% and is advantageously between 0.01% and 0.5% by weight. For the purposes of the present invention, the term "polyelectrolyte reactive with polyvalent ions" means a polyelectrolyte capable of passing from a liquid state in an aqueous solution to a gelled state under the effect of contact with a gelling solution containing multivalent ions such as ions of an alkaline earth metal chosen for example from calcium ions, barium ions, magnesium ions. In the liquid state, the individual polyelectrolyte chains are substantially free to flow relative to one another. An aqueous solution of 2% by weight of polyelectrolyte then exhibits a purely viscous behavior at the shear gradients characteristic of the forming process. The viscosity of this zero shear solution is between 50 mPa.s and 10,000 mPa.s, advantageously between 3000 mPa.s and 7000 mPa.s. The individual polyelectrolyte chains in the liquid state advantageously have a molar mass greater than 65000 g / mol. In the gelled state, the individual polyelectrolyte chains form, with the multivalent ions, a coherent three-dimensional network that retains the liquid core and prevents its flow. The individual chains are held together and can not flow freely relative to each other. In this state, the viscosity of the formed gel is infinite. In addition, the gel has a threshold of stress to the flow. This stress threshold is greater than 0.05 Pa. The gel also has a modulus of elasticity that is non-zero and greater than 35 kPa. The three-dimensional gel of polyelectrolyte contained in the envelope traps water and the surfactant. The polyelectrolyte is preferably a biocompatible polymer that is harmless to the human body. It is for example produced biologically.

Advantageously, it is chosen from polysaccharides, synthetic polyelectrolytes based on acrylates (sodium, lithium, potassium or ammonium polyacrylate, or polyacrylamide), synthetic polyelectrolytes based on sulfonates (poly (styrene sulfonate)). sodium, for example). More particularly, the polyelectrolyte is selected from an alkaline earth alginate, such as sodium alginate or potassium alginate, gellan or pectin.

Alginates are produced from brown algae called "laminar", referred to as "sea weed". Such alginates advantageously have a content of α-L-guluronate greater than about 50%, preferably greater than 55%, or even greater than 60%.

In particular, the or each polyelectrolyte will be a polyelectrolyte reactive with multivalent ions, in particular a polysaccharide reactive with multivalent ions such as an alkali alginate, a gelane or a pectin, preferably an alkali metal alginate advantageously having a bulk content aL-guluronate greater than 50%, especially greater than 55%.

More particularly, the mass content of polyelectrolyte in the second solution may be less than 5% by weight and is advantageously between 0.5 and 3% by weight. According to one aspect of the present invention, the capsule may further comprise an intermediate envelope completely encapsulating at its periphery the liquid core, said intermediate envelope itself being encapsulated completely at its periphery by the gelled envelope. This liquid intermediate envelope will be formed of an intermediate composition comprising a buffer or a cell culture medium, and / or a viscosifier. In particular, the viscosifier will be a water-soluble polymer, such as PEG, dextran or alginate in solution more diluted than in the outer shell. The intermediate envelope is in contact with the core and the outer envelope and keeps the core out of contact with the outer envelope. The intermediate phase is useful for stabilizing the capsule during its formation, for example in the case where the liquid core contains calcium capable of inducing gelation of the external phase too early. Indeed, depending on their composition, the cell culture media can interfere with the polymerization. It thus makes it possible to separate the liquid core from the external phase to be gelated. It also protects the liquid heart containing the cells during the formation of drops, alginate of the outer layer which has not yet polymerized.

In particular, the liquid core and the intermediate phase being both liquid, they are eventually mixed to form the liquid core of the capsule. The presence of such an intermediate envelope is described in particular in the scientific article "Formation of liquid-core capsules having a thin hydrogel membrane: liquid pearls", Bremond et al, Soft Matter, 2010, 2484-2488.35 Production of drops Production drops according to the method according to the invention mentioned above is carried out by separate conveying in a double jacket of a first liquid solution containing the cell or cells with hematopoietic potentiality and a second liquid solution containing a liquid polyelectrolyte suitable for gelling and minus a surfactant, as described in WO2010 / 063937. In the case of the additional presence of an intermediate envelope, the separated conveying takes place in a triple envelope, with a third solution comprising the intermediate solution.

At the exit of the double (or triple) envelope, the different flows come into contact and then form a multi-component drop, according to a hydrodynamic mode called "dripping" (drop-by-drop, described in particular in WO 2010 / 063937) or a mode called "jetting" (with jet instability, described in particular in FR 2012/2964017), depending on the size of the desired capsules.

The first flow constitutes the liquid core and the second flow constitutes the liquid outer envelope. In the case of the presence of the intermediate envelope, the second flux constitutes the liquid intermediate envelope and the third flux the external liquid envelope. According to the production method, each multi-component drop is detached from the double (or triple) envelope and falls into a volume of air, before being immersed in a gelling solution containing a reagent capable of gelling the polyelectrolyte of the outer liquid envelope, to form the outer gelled envelope of the capsules according to the invention. According to some embodiments, the multi-component drops may comprise additional layers between the outer envelope and the liquid core, other than the intermediate envelope. This type of drop may be prepared by separate conveying of multiple compositions into multi-envelope devices. Gel step When the multi-component drop comes into contact with the gelling solution, the reagent capable of gelling the polyelectrolyte present in the gelling solution then forms bonds between the various polyelectrolyte chains present in the liquid outer envelope, then moving to the gelled state, thus causing the gelling of the liquid outer shell. Without wishing to be bound to a particular theory, during the transition to the gelled state of the polyelectrolyte, the individual polyelectrolyte chains present in the liquid outer envelope are connected to each other to form a crosslinked network, also called hydrogel.

In the context of the present description, the polyelectrolyte present in the gelled outer shell is in the gelled state and is also called gelled polyelectrolyte or gelled polyelectrolyte. A gelled outer envelope, adapted to retain the assembly constituted by the heart or the core and the intermediate envelope, is thus formed. This outer gelled envelope has a clean mechanical strength, that is to say that it is able to retain the liquid core and, in case of presence of an intermediate envelope, to completely surround the intermediate envelope. This has the effect of maintaining the internal structure of the liquid core and, where appropriate, the intermediate envelope.

The capsules according to the invention remain in the gelling solution until the outer shell is completely gelled, preferably without exceeding 30 minutes, even more preferably without exceeding 5 minutes. The gelling solution can then optionally be removed and the gelled capsules can then optionally be collected and immersed in an aqueous rinsing solution, generally consisting essentially of water, in particular of physiological saline, in order to rinse off the gelled capsules formed. This rinsing step makes it possible to extract from the gelled external envelope any excess of the reagent suitable for gelling the gelling solution, and all or part of the surfactant (or other species) initially contained in the second liquid solution.

The presence of a surfactant in the second liquid solution makes it possible to improve the formation and gelation of the multi-component drops according to the process as described above. Characteristics of gelled capsules Advantageously, the capsule is spherical in shape and has an outside diameter of less than 5 mm and in particular between 0.3 mm and 3 mm. Preferably, the gelled outer shell of the capsules according to the invention has a thickness of from 10 .mu.m to 500 .mu.m, preferably from 20 .mu.m to 200 .mu.m, and advantageously from 50 .mu.m to 100 .mu.m. The fineness of the thickness of the outer gelled envelope generally makes this outer envelope transparent. The capsules according to the invention generally have a volume ratio between the core and all of the intermediate and outer shells greater than 2, and preferably less than 50. According to one particular embodiment, the capsules according to the invention generally have a volume ratio between the core and the set of intermediate and outer envelopes between 5 and 10.

The invention also relates to the use of at least one capsule as described in the context of the present invention, for the ex vivo production of enucleated erythroid cells, in particular reticulocytes and / or erythrocytes.

It also relates to an ex vivo method for producing enucleated erythroid cells comprising culturing hematopoietic potential cells contained in at least one capsule as defined in the context of the present invention, under conditions allowing the production of enucleated erythroid cells. In particular, the enucleated erythroid cells produced according to the method of the present invention are reticulocytes and / or erythrocytes. In particular, the cells with hematopoietic potentiality used in the context of the method according to the invention are hematopoietic stem cells and / or erythroid progenitor cells and / or erythroid precursors, more particularly human.

Thus, cells with hematopoietic potentiality can be cultured in the context of the present invention in a culture medium comprising: a) insulin at a concentration of between 1 and 50 μg / ml; b) transferrin at a concentration of between 100 and 2000 μg / ml; and c) plasma or serum at a concentration of between 1 and 30%. "Culture medium" means any medium, in particular any liquid medium, capable of supporting the growth of cells with hematopoietic potential, in particular hematopoietic stem cells, erythroid progenitor cells and erythroid precursors, more particularly human, and to allow the production of enucleated erythroid cells, particularly reticulocytes and / or erythrocytes. The insulin of the culture medium according to the present invention is, in particular, recombinant human insulin. Its concentration is preferably between 5 and 20 μg / ml, more preferably between 8 and 12 μg / ml, and still more preferably between 10 μg / ml. The transferrin of the culture medium according to the invention is, in particular, human transferrin. More particularly, transferrin is saturated with iron. Its concentration is preferably between 200 and 1000 μg / ml, more preferably between 300 and 500 μg / ml, and still more preferably between 330 and 450 μg / ml. Transferrin may also be in recombinant form.

The plasma or the serum of the culture medium according to the invention are, in particular, human. Their concentration is preferably between 1 and 20%, more preferably between 4 and 12%, and even more preferably 5 or 10%. According to one aspect of the present invention, the culture medium also comprises heparin, in particular at a concentration of between 0.5 and 5 IU / ml, preferably between 1.5 and 3.5 IU / ml, and also more preferably 2 IU / ml. In particular, the culture medium according to the present invention comprises heparin when the culture medium also comprises plasma. The culture medium may also comprise EPO and / or SCF and / or IL-3 and / or hydrocortisone. The EPO (erythropoietin) of the culture medium according to the invention is, in particular, recombinant human EPO. Its concentration is preferably between 0.5 and 20 IU / ml, more preferably between 2.5 and 3.5 IU / ml, and still more preferably with 3 IU / ml.

The SCF (Stem Cell Factor) of the culture medium according to the invention is, in particular, recombinant human SCF. Its concentration is preferably between 50 and 200 ng / ml, more preferably between 80 and 120 ng / ml, and even more preferably 100 ng / ml. IL-3 (interleukin 3) of the culture medium according to the invention is, in particular, recombinant human IL-3. Its concentration is preferably between 1 and 30 ng / ml, more preferably between 4 and 6 ng / ml, and still more preferably 5 ng / ml. Hydrocortisone, which is optionally added to the culture medium, according to the invention preferably has a concentration of between 5.10-7 and 5.10-6 M, and more preferentially of 5.10-6 M. According to one aspect of the present invention, the culture medium may also comprise at least one of the following compounds: TPO, FLT3, BMP4, VEGF-A165 and IL-6. The TPO (thrombopoietin) of the culture medium according to the invention is, in particular, recombinant human TPO. Its concentration is preferably between 20 and 200 ng / ml, more preferably between 80 and 120 ng / ml, and even more preferably 100 ng / ml. The FLT3 (FMS-like tyrosine kinase 3 ligand) of the culture medium according to the invention is, in particular, recombinant human FLT3. Its concentration is preferably between 20 and 200 ng / ml, more preferably between 80 and 120 ng / ml, and even more preferably 100 ng / ml.

The BMP4 (Bone Morphogenic Protein 4) of the culture medium according to the invention is, in particular, recombinant human BMP4. Its concentration is preferably between 1 and 20 ng / ml, more preferably between 8 and 12 ng / ml, and still more preferably with 10 ng / ml.

VEGF-A165 (Vascular Endothelial Growth Factor A165) of the culture medium according to the invention is, in particular, recombinant human VEGF-A165. Its concentration is preferably between 1 and 20 ng / ml, more preferably between 4 and 6 ng / ml, and still more preferably with 5 ng / ml. IL-6 (interleukin 6) of the culture medium according to the invention is, in particular, recombinant human IL-6. Its concentration is preferably between 1 and 20 ng / ml, more preferably between 4 and 6 ng / ml, and still more preferably with 5 ng / ml. In the context of the present invention, the culture medium comprises a base culture medium, the latter having the characteristic of being able to support the growth of cells with hematopoietic potential, in particular hematopoietic stem cells, progenitor cells erythroid and / or erythroid precursors, more particularly human, and allow the production of enucleated erythroid cells, particularly reticulocytes and / or erythrocytes. This type of basic culture medium is well known to those skilled in the art. For example, Iscove Dulbecco modified medium (IMDM), supplemented with glutamine or a peptide containing glutamine. Thus, the culture medium according to the present invention also preferably comprises modified Iscove Dulbecco medium supplemented with glutamine or a peptide containing glutamine.

In particular, cells with hematopoietic potentiality are cultured in a medium comprising: during a first step of 5 to 9 days, in particular 7 days: insulin at a concentration of between 8 and 12 μg / ml; transferrin at a concentration of between 300 and 350 μg / ml; plasma at a concentration of between 3 and 7%; heparin at a concentration of between 1.5 and 2.5 IU / ml; - Optionally, hydrocortisone at a concentration between 5.10-7 and 5.10-6 M; - SCF at a concentration of between 80 and 120 ng / ml; IL-3 at a concentration of between 4 and 6 ng / ml; and EPO at a concentration of between 2.5 and 3.5 μl / ml; then in a second step of 0 to 5 days, in particular 3 to 4 days: insulin at a concentration of between 8 and 12 μg / ml; transferrin at a concentration of between 300 and 350 μg / ml; plasma at a concentration of between 3 and 7%; heparin at a concentration of between 1.5 and 2.5 IU / ml; optionally hydrocortisone at a concentration of between 5.10-7 and 5.10-6 M; - SCF at a concentration of between 80 and 120 ng / ml; and EPO at a concentration of between 2.5 and 3.5 μl / ml; and in a third step of 6 to 10 days, in particular up to 18 or 21 days since the beginning of the first step: insulin at a concentration of between 8 and 12 μg / ml; transferrin at a concentration of between 300 and 350 μg / ml; plasma at a concentration of between 3 and 7%; heparin at a concentration of between 1.5 and 2.5 IU / ml; and EPO at a concentration of between 2.5 and 3.5 μl / ml. Alternatively, the cells with hematopoietic potentiality are cultured in a medium comprising: during a first step of 6 to 8 days, in particular 7 days: insulin at a concentration of between 8 and 12 μg / ml; transferrin at a concentration of between 300 and 350 μg / ml; plasma at a concentration of between 1% and 7%; heparin at a concentration of between 1.5 and 2.5 IU / ml; SCF at a concentration of 80 to 120 ng / ml; IL-3 at a concentration of between 5 and 30 ng / ml; TPO at a concentration of 80 to 120 ng / ml; and FLT3 at a concentration of between 30 and 60 ng / ml; then in a second step of 10 to 16 days, in particular 14 days: insulin at a concentration of between 8 and 12 μg / ml; transferrin at a concentration of between 300 and 350 μg / ml; plasma at a concentration of between 1% and 7%; heparin at a concentration of between 1.5 and 2.5 IU / ml; optionally hydrocortisone at a concentration of between 5.10-7 and 5.10-6 M; - SCF at a concentration of between 80 and 120 ng / ml; EPO at a concentration of 2.5 to 3.5 μl / ml; and IL-3 at a concentration of between 4 and 6 ng / ml; and in a third step of 6 to 12 days, particularly up to 28 or 32 days from the beginning of the first step: insulin at a concentration of between 8 and 12 μg / ml; transferrin at a concentration of between 300 and 350 μg / ml; plasma at a concentration of between 1% and 7%; heparin at a concentration of between 1.5 and 2.5 IU / ml; and EPO at a concentration of 2.5 to 3.5 Ili / ml.

Alternatively, the cells with hematopoietic potentiality are cultured in a medium comprising: during a first step of 5 to 25 days, in particular 20 days: insulin at a concentration of between 8 and 12 μg / ml; transferrin at a concentration of between 425 and 475 μg / ml; plasma at a concentration of between 3 and 7%; heparin at a concentration of between 1.5 and 2.5 IU / ml; - SCF at a concentration of between 80 and 120 ng / ml; TPO at a concentration of between 80 and 120 ng / ml; FLT3 at a concentration of between 80 and 120 ng / ml; - BPM4 at a concentration of between 8 and 12 ng / ml; - VEGF-A165 at a concentration between 4 and 6 ng / ml. IL-3 at a concentration of between 4 and 6 ng / ml; IL-6 at a concentration of between 4 and 6 ng / ml; and EPO at a concentration of between 2.5 and 3.5 μl / ml; then during a second step of 6 to 10 days, in particular 8 days: insulin at a concentration of between 8 and 12 μg / ml; transferrin at a concentration of between 425 and 475 μg / ml; plasma at a concentration of between 8 and 12%; heparin at a concentration of between 2.5 and 3.5 IU / ml; - SCF at a concentration of between 80 and 120 ng / ml; IL-3 at a concentration of between 4 and 6 ng / ml; and EPO at a concentration of between 2.5 and 3.5 μl / ml; then in a third step of 2 to 4 days, in particular 3 days: insulin at a concentration of between 8 and 12 μg / ml; transferrin at a concentration of between 425 and 475 μg / ml; plasma at a concentration of between 8 and 12%; heparin at a concentration of between 2.5 and 3.5 IU / ml; - SCF at a concentration of between 80 and 120 ng / ml; and EPO at a concentration of between 2.5 and 3.5 μl / ml; and in a fourth step from 10 to 16 days, particularly 13 days: insulin at a concentration of between 8 and 12 μg / ml; transferrin at a concentration of between 425 and 475 μg / ml; plasma at a concentration of between 8 and 12%; heparin at a concentration of between 2.5 and 3.5 IU / ml; and EPO at a concentration of between 2.5 and 3.5 μl / ml. In the context of the present invention, the cells are preferably encapsulated at OJ, that is to say at a very early stage of differentiation, for example that of hematopoietic stem cells, but may also be encapsulated at a later stage. that is, at the stage of progenitor or erythroid precursor.

The capsules according to the invention comprising at least one cell with hematopoietic potential, may therefore comprise only poorly differentiated cells such as hematopoietic stem cells, only cells with a more advanced differentiation stage such as erythroid progenitor cells, erythroid precursors or a mixture of hematopoietic potential cells at different stages of differentiation. The present invention will be further illustrated by the following figures and examples which do not limit the scope thereof. FIGURES FIG. 1: Principle of the preparation of the capsules: A triple-envelope structure is represented in which the fluid constituting the core (which comprises at least one cell with hematopoietic potentiality) is introduced into the central envelope indicated by the vertical arrow while the intermediate fluid is introduced into the intermediate envelope indicated by the arrow to the left of the triple-shell structure and the fluid of the shell into the outer envelope indicated by the arrow to the right of the triple-shell structure. The capsules thus formed fall into the gelling bath. Figure 2: Perspective view of the injector. Figure 3: Section view of the injector: The injector comprises three inputs, the first input located on the left of the sectional view corresponding to the inlet of the intermediate fluid, the second input corresponding to the first input located on the above the sectional view corresponding to the inlet of the core fluid and the third inlet corresponding to the second inlet located on the top of the sectional view corresponding to the inlet of the shell fluid. Figure 4: Encapsulation of the cells.

EXAMPLE Culture of Encapsulated Hematopoietic Potential Cells Cell Preparation CD34 + cells are isolated from placental blood by selection using supermagnetic microbeads using Mini-MACS columns (Miltenyi Biotech, Bergisch Glodbach, Germany) (> 94 purity). ± 3%). The cells are cultured in IMDM medium (Iscove modified Dulbecco's, Biochrom, Germany) supplemented with 2 mM L-glutamine (Invitrogen, Cergy-Pontoise, France), 330 μg / ml iron-saturated human transferrin, 10 μg / ml of insulin (Sigma, Saint-Quentin Fallavier, France), 2 Ili / mi of heparin Choay (Sanofi, France) and 5% of plasma (solvent / detergent inactivated plasma virus (S / D)). 104 CD34 + / ml cells are cultured in the presence of 100 ng / ml SCF (supplied by Amgen, Thousand Oaks, CA), 5 ng / ml IL-3 (R & D Systems, Abingdon, UK) and 3 Ili EPO / mi (Eprex, supplied by Janssen Cilag, Issy-les-Moulineaux, France). At day 4, a cell culture volume is diluted in four volumes of fresh medium containing SCF, IL-3 and EPO. The cultures are maintained at 37 ° C with 5% CO2 in the air. At day 8, the cells are counted and their concentration is adjusted in the encapsulation medium (IMDM, heparin, plasma, insulin, transferrin, EPO, SCF and IL-3) in order to reach the desired concentration. The cells are encapsulated on D8. Cell Encapsulation Protocol The general principle of capsule formation is shown in Figure 1. The day before the encapsulation procedure, the following elements were prepared. One liter of 1% CaCl 2 was filtered through a 0.2 μm filter to serve as a gelling bath. Two liters of physiological saline (0.9% NaCl) are prepared which will be used to rinse the set up, ie the injector, the tubes, the syringes and the connectors forming the encapsulation device, as well as than the capsules. A liter of milliQ water is also prepared for setting up the set up under water. Finally, a solution of 30 ml of 2% alginate with 0.5 mM SDS is prepared. The following elements were autoclaved: crystallizer, 10 beakers of 150m1 (to recover the capsules and rinse them), forceps, microfluidic connectors (for 1/16 inch tube diameter), Teflon tubes (1/16 diameter) inch, 60 cm). The following day, the encapsulation device is mounted according to the following procedure: the set up is washed with 70% EtOH and then with filtered milliQ water. (injector XII see Figures 2 and 3). It includes capillaries with an internal diameter of 0.78 mm and an external diameter of 1 mm, as well as 3 SGE syringes (VWR) and internal 5 ml with agitation, while those for the other two 10 ml phases. The set up is mounted under water to avoid the presence of bubbles and then filled with PBS / SVF (fetal calf serum) 10% and left for one hour to prevent the cells from sticking to the walls of the tubes or the injector thereafter. It is then rinsed with physiological water. The intermediate phase circuit is washed with IMDM (Iscove's Modified Dulbecco's Medium) while the internal phase circuit is washed with culture medium containing IMDM, heparin and plasma. The final set up is put in place with a solution of alginate 2% for the shell of the IMDM for the intermediate phase and with a cell suspension comprising between 1.25 × 10 5 cells / mi and 2.5 × 10 5 cells / mi in a medium whole culture containing IMDM, heparin, plasma, insulin, transferrin, EPO, SCF and IL-3 for the inner phase. The encapsulation is carried out as indicated in FIG. 4 by a drip encapsulation (dripping) method. The flow rates used for the different internal-intermediate-shell phases are respectively 5, 1 and 3 ml / h. The formation time of the capsule is 4.9 seconds. The resulting capsules are 1.6 mm in diameter. They consist of an external phase which will be gelled in the presence of calcium, an intermediate phase intended to stabilize the capsule during its formation, and an internal phase containing the cells.

The gelation step is then carried out with a gelling bath containing a solution of calcium chloride and a drop of Tween 20 ® at 10%. From 20 to 30 capsules are immersed in the gelling bath. Capsules containing the cells should not remain in the bath for more than five minutes. The calcium solution is then removed without dropping the capsules and they are rinsed with 3x30 ml of physiological saline. The physiological water is then removed while the capsules are resuspended in 10 ml of culture medium. The whole is then transferred to a culture flask of 25 cm2. For the capsules to be well immersed, the bottles are placed vertically. The cells are then cultured in fresh medium in the presence of EPO until J19. The cultures are maintained at 37 ° C with 5% CO2 in the air.

Results The results are shown in Table 1 below. Table 1 nb cells / capsule Rate of Enucleation Fraction Rate [volume fraction multiplication final cell death (J19)] J8 to J19 (Trypan Blue) 850 [0.03%] 705 42% 8% 2% 850 [0,03%] 579 62% 8% 2% 1650 [0,06%] 352 47% 14% 2,5% 1650 [0,06%] 354 61% 15% 2,5% Classical culture (in 585 70% 10% 0.1% vial) [0.01%] The encapsulated cells are red in color, indicating the presence of hemoglobin. The encapsulated cells are observed after dissolution of the capsule and May-Grünwald Giemsa staining. The presence of mitotic cells, few apoptotic cells and few vacuolar cells is observed. A volume fraction of 2% cells in the capsules is obtained after three weeks of culture, and a viability equivalent to that measured in static culture. Thus, the capsules containing cells with hematopoietic potentiality according to the invention make it possible to envisage for the first time an application to cell culture of cells with hematopoietic potentiality on a large scale.

Claims (11)

REVENDICATIONS1. Capsule comprising a liquid core, a gelled envelope completely encapsulating the liquid core at its periphery, the gelled envelope being adapted to retain the liquid core when the capsule is immersed in a gas, the gelled envelope comprising at least one gelled polyelectrolyte and at minus a surfactant, characterized in that the liquid core comprises at least one cell with hematopoietic potentiality. 2. Capsule according to claim 1, characterized in that it is obtained by the implementation of a method comprising the following steps of: a) separate conveying in a double jacket of a first physiologically acceptable liquid solution containing at least a hematopoietic potential cell and a second liquid solution containing a liquid polyelectrolyte suitable for gelation; b) forming, at the exit of the jacket, a series of drops, each drop comprising a central core formed of said first solution and a peripheral film formed of said second solution and completely covering the central core; c) immersing each drop in a gelling solution containing a reagent adapted to react with the polyelectrolyte of the film to change it from a liquid state to a gelled state and form the gelled envelope, the central core forming the liquid core; d) recovery of formed capsules; the second solution containing at least one surfactant prior to contact with the first solution. 3. Capsule according to claim 2, characterized in that the ratio of the flow rate of the first solution to the flow rate of the second solution at the outlet of the jacket is between 1 and 200, preferably between 10 and 200, the gelled envelope having a thickness of between 0.1% and 10%, advantageously between 0.1% and 2% of the diameter of the capsule, after recovery of the capsules formed. 4. Capsule according to any one of claims 2 or 3, characterized in that the drops formed by coextrusion in the jacket fall by gravity through a volume of air in the gelling solution. 5. Capsule according to any one of claims 2 to 4, characterized in that the first physiologically acceptable liquid solution comprises a saline solution, a buffer solution, a physiologically acceptable viscosifier, a physiologically acceptable excipient, preferably a thickener or a modifier of rheology, and / or culture medium. 6. Capsule according to any one of claims 1 to 5, characterized in that it further comprises an intermediate envelope completely encapsulating at its periphery the liquid core, said intermediate envelope itself being encapsulated completely at its periphery by the gelled envelope. 7. Capsule according to any one of claims 1 to 6, characterized in that said at least one hematopoietic potential cell is a hematopoietic stem cell and / or an erythroid progenitor cell and / or an erythroid precursor. 8. Capsule according to any one of claims 1 to 7, characterized in that said at least one cell with hematopoietic potential or hematopoietic stem cell or erythroid progenitor cell or erythroid precursor is a cell or a human precursor. 9. Use of at least one capsule according to any one of claims 1 to 8 for the ex vivo production of enucleated erythroid cells. 10. Use according to claim 9, characterized in that the enucleated erythroid cells are reticulocytes and / or erythrocytes. An ex vivo method for producing enucleated erythroid cells comprising culturing hematopoietic potential cells contained in at least one capsule as defined in any one of claims 1 to 8, under conditions permitting the production of enucleated erythroid cells. 25. The method according to claim 11, characterized in that the cells with hematopoietic potentiality are cultured in a culture medium comprising: e) insulin at a concentration of between 1 and 50 μg / ml; f) transferrin at a concentration of between 100 and 2000 μg / ml; and g) plasma or serum at a concentration of between 1 and 30%. 13. The method of claim 12, characterized in that the culture medium also comprises EPO and / or SCF and / or IL-3 and / or hydrocortisone. 14. Method according to any one of claims 12 or 13, characterized in that the culture medium also comprises at least one of the following compounds: TPO, FLT3, BMP4, VEGF-A165 and IL-6. 15. Method according to any one of claims 12 to 14, characterized in that the culture medium also comprises modified Iscove Dulbecco medium supplemented with glutamine or a peptide containing glutamine. 16. Method according to any one of claims 11 to 15, characterized in that the enucleated erythroid cells are reticulocytes and / or erythrocytes. 17. Method according to any one of claims 11 to 16, characterized in that the cells with hematopoietic potential are hematopoietic stem cells and / or erythroid progenitor cells and / or erythroid precursors.